JPH0895317A - Image forming device - Google Patents

Abstract

PURPOSE: To make it possible to maintain the electrostatic charging potential of a photoreceptor at a specified value at all times regardless of use environment and fluctuation with lapse of time. CONSTITUTION: A correction rule changeover menas D changes over a correction rule by an impressed voltage correcting means C according to the change rate with lapse of time detected by a means B for detecting the change with lapse of time. The impressed voltage correcting means C corrects the impressed voltage on an electrostatic charging member according to the detection temp. of a temp. detecting means A by referring to the correction rule. A light quantity correcting means E electrostatically charges the surface of the photoreceptor by impression of the voltage on the electrostatic charging member. The photoreceptor is thereafter exposed by an exposure device to form a reference potential pattern and the potential thereof is detected. The surface of the photoreceptor is electrostatically charged by correcting the light quantity of the exposure device at the time of image forming process and is then destaticized. The residual potential is detected and the electrostatic charge potential of the surface of the photoreceptor or the developing bias of a developing roller is corrected at the time of image forming process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic photography type image forming apparatus such as a laser printer, a copying machine, a facsimile machine, etc., and more particularly, a charging member is brought into contact with a rotating photosensitive member to charge its surface. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In an electrostatic image forming apparatus such as a copying machine, the surface of a drum-shaped or belt-shaped photosensitive member is uniformly charged by a charger and then exposed by an exposure device to be electrostatically charged. A latent image is formed, and the latent image is visualized by attaching toner with a developing roller in a developing device, and then transferred to a transfer paper fed from a paper feeding section by a transfer device, and then transferred by a fixing device. The toner is fixed and discharged, and the residual toner on the surface of the photoconductor is removed by a cleaning device.

By the way, in a conventional electrostatic image forming apparatus, a corona discharge method which is a non-contact method has been used in order to uniformly charge a photosensitive member. A large amount of ozone was generated to charge the photoconductor. This ozone is generated more often when a negative discharge is performed, but it is a serious problem along with the fact that the photoreceptor has become an organic photoreceptor for negative charging in recent years and the environmental standard for generated gas has become strict. Has become. Further, there is also a problem that non-uniform charging is caused by adhesion of nitrogen oxides (NOx) secondarily generated by ozone to the discharger.

Therefore, in order to solve these problems, a contact charging type image forming apparatus has recently been developed in which a charging member such as a charging roller to which a voltage is applied is brought into contact with the surface of the photoconductor to charge the surface of the photoconductor. Has been done. In this image forming apparatus, since the surface of the photoconductor is charged by the discharge through the gap existing between the photoconductor and the charging member, the applied voltage can be lowered as compared with the corona discharge, and the ozone generation amount is drastically reduced. To have.

[0005]

However, in such an image forming apparatus, the required charging potential cannot be obtained because the resistance value and the dielectric constant of the charging member change depending on the environment of use, which causes uneven charging. Was there. Therefore, JP-A-4
As disclosed in Japanese Patent Application Laid-Open No. 186381, there has been proposed one in which uneven charging is prevented by detecting the temperature of the charging member and varying the voltage applied to the charging member according to the detected temperature. Since the temperature dependence of the surface potential of the photoconductor is not proportional to the voltage applied to the charging member, it is difficult to completely prevent uneven charging.

There is also a problem that the charging potential of the photoconductor fluctuates due to film loss of the photoconductive layer caused by friction of the photoconductive film of the photoconductor. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 5-27557, the amount of film loss of the photoconductor is detected, and the voltage applied to the charging member is lowered in accordance with the increase in the amount, whereby the charging potential of the photoconductor is set to a predetermined value. Although it has been proposed to keep the value at a constant value, the effect of film loss of the photoconductor is opposite at high temperature and at low temperature, so the charging potential cannot always be kept at a constant value.

Further, when a charging roller is used as the charging member, the charging roller generally has a diameter much smaller than that of the photosensitive member for the purpose of downsizing, so that it does not pose a problem on the image. Even a small amount of dirt that adheres to the toner after passing through such a cleaning device becomes a large dirt due to an increase in the frequency of adhesion, causing a partial charging failure.

The present invention has been made in view of the above points, and it is an object of the present invention to always maintain the charging potential of a photosensitive member at a constant value regardless of the use environment and the temporal change, and to stabilize the image quality. To do.

[0009]

In order to achieve the above-mentioned object, the present invention achieves the above object, a photoconductor that rotates, a charging member that contacts the photoconductor to uniformly charge the surface thereof, and a charging member that charges the surface. An exposure device that exposes the surface of the photoconductor to form an electrostatic latent image, a developing device that visualizes the latent image by attaching toner with a developing roller, and the visualized toner image is transferred. An electrophotographic image forming apparatus including a transfer device for transferring onto paper and a cleaning member for cleaning the surface of a charging member is provided with the following respective means.

That is, as shown in the functional block diagram of FIG. 1, temperature detecting means A for detecting the temperature of the charging member, time-dependent change detecting means B for detecting the time-dependent change of the photosensitive member, and temperature detecting means A for detecting. The applied voltage correction means C for correcting the applied voltage to the charging member according to the temperature, and the correction rule of the applied voltage according to the detected temperature by the means C are provided according to the amount of change with time detected by the change with time detecting means B. After the surface of the photoconductor is charged by applying the voltage corrected by the correction rule switching means D and the applied voltage correction means C to the charging member, the exposure device exposes the reference potential pattern to form the potential. And a light quantity correction means E for detecting the light quantity and correcting the light quantity of the exposure device during the image forming process.

Further, the voltage corrected by the applied voltage correction means C is applied to the charging member to charge the surface of the photoconductor and then the charge is removed, and the residual potential is detected to charge the surface of the photoconductor during the image forming process. It is preferable to provide a potential correction means F for correcting the potential or the developing bias of the developing roller.

Further, in the correction rule switching means D, when the time-dependent change amount detected by the time-dependent change detecting means B after the completion of the image forming job exceeds a predetermined amount, a temperature detected by the applied voltage correcting means C is detected. The means for switching the correction rule of the applied voltage according to the above, the applied voltage correction means C is used to switch the correction rule by the correction rule switching means D, and then the detected temperature of the temperature detection means A is referred to with reference to the correction rule. Therefore, a means for correcting the voltage applied to the charging member may be used.

Furthermore, it is desirable to provide a means for cleaning the charging member with a cleaning member before the correction processing by the light amount correction means E and the potential correction means F is performed. Further, it is preferable to provide a means for cleaning the charging member with the cleaning member when the temperature detected by the temperature detecting means A falls below a predetermined threshold value.

Further, when the light amount correcting means E and the potential correcting means F detect the temperature detected by the temperature detecting means A below a predetermined threshold value, or when the detected temperature exceeds the predetermined threshold value after the temperature falls below the predetermined threshold value. A correction process may be performed.

[0015]

In the image forming apparatus of the present invention, the correction rule switching means D of FIG. 1 switches the correction rule by the applied voltage correction means C in accordance with the amount of change over time detected by the change detection means B, and the applied voltage correction means. C corrects the voltage applied to the charging member according to the temperature detected by the temperature detecting means A by referring to the correction rule, and charges the surface of the photoconductor by applying the corrected voltage to the charging member. Correction means E
Forms a reference potential pattern by exposing with an exposure device, and detects the potential to correct the light amount of the exposure device during the image forming process.For example, when a selenium-based photoconductor is used, Regardless of the environment (usage environment) or the change over time, the charged potential of the photoconductor can always be maintained at a constant value, and stable image quality can be obtained.

Further, the potential correction means F applies the voltage corrected by the applied voltage correction means C to the charging member to charge the surface of the photosensitive member and then removes the charge, and the residual potential is detected to perform the image forming process. If the charge potential on the surface of the photoconductor or the developing bias of the developing roller is corrected, even when an OPC (organic photoconductor) -based photoconductor is used, the same as the above, regardless of the in-machine environment and the temporal change. The charging potential of the photoconductor can be always maintained at a constant value.

Further, when the temporal change amount detected by the temporal change detecting means B after the image forming job is over a predetermined amount, the correction rule switching means D switches the correction rule by the applied voltage correcting means C. If the applied voltage correction means C then corrects the applied voltage to the charging member according to the temperature detected by the temperature detection means A with reference to the correction rule, the photoconductor will be activated even when the correction rule is switched. Since the charging potential of 1 does not change, more stable image quality can be obtained.

Furthermore, if the charging member is cleaned by the cleaning member before the correction processing by the light amount correcting means E and the potential correcting means F is performed, the charging member is prevented from being contaminated with the toner and the charging failure is reduced. In addition, a more stable image quality can be obtained. Also,
If the cleaning member cleans the charging member when the temperature detected by the temperature detecting means A falls below a predetermined threshold value, a new mechanism does not detect the in-machine environment, and the environment changes due to an inexpensive configuration. It is possible to effectively prevent the charging member from being soiled.

Further, if the light amount correction means E and the potential correction means F perform the above correction processing when the temperature detected by the temperature detection means A falls below a predetermined threshold value, the sensitivity of the photoconductor at a low temperature. It is possible to prevent the image from being shifted to the dark side due to the decrease of. Alternatively, if the light quantity correction means E and the potential correction means F perform the above correction processing when the temperature detected by the temperature detection means A exceeds a predetermined threshold value and then exceeds the threshold value, the change in the in-machine environment It is possible to prevent image fluctuation due to

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the periphery of a drum of a copying machine which is an embodiment of the present invention.

In this copying machine, a photosensitive drum 1 which is a member to be charged is directly contacted with a charging roller 2 which is a charging member and a preset voltage is applied to the photosensitive member 1 so that the photosensitive member 1 is rotated. 1 is a contact charging type copier that uniformly charges the surface 1a of the photosensitive drum 1 to a predetermined potential, and the photoconductor 1 rotates in the direction of arrow A at a predetermined peripheral speed, and the charging roller 2 rotates while making contact with it. Will rotate at a constant speed in the direction of the arrow.

The photosensitive member 1 is driven by a driving device including a drum driving timing belt, a drum driving pulley, a motor (not shown) for driving the drum driving pulley, etc., and the charging roller 2 is always provided on the surface 1a. Are in contact with each other with a predetermined pressure. Around the photoconductor 1, in addition to the charging roller 2, the eraser 3, the developing device 4, the endless belt 7a.
A contact type transfer device 7, a P sensor 8, a cleaning unit 9, and a quenching lamp 10 are sequentially arranged.

In a normal image forming process, the surface 1a of the photosensitive member 1 is charged by the charging roller 2 to a predetermined potential (-900 V in this example), and the charged surface is exposed by the exposure device 11 (only the mirror portion is shown in FIG. (Shown) to form an electrostatic latent image by exposure to light corresponding to the original image from the original image, and the electrostatic latent image is subjected to electrostatic charge in an area portion outside the size of the transfer paper P used by the eraser 3. Removal (trimming)
Then, the remaining electrostatic latent image is visualized (developed) by the toner supplied by the developing roller (developing sleeve) 4a of the developing device 4.

On the other hand, the transfer paper in the paper feed cassette (not shown) is moved by a paper feed roller which rotates at a predetermined timing.
The image is sent out one by one, and is temporarily stopped between the registration roller 12 and the pressure roller 13 that rotates in pressure contact with the registration roller 12 to adjust the timing, and then the transfer device 7 is set at an accurate timing that matches the toner image on the photoconductor 1. The sheet is fed toward the transfer section where is provided.

Then, a transfer bias is applied to the transfer paper P by the transfer device 7 to transfer the toner image on the upper surface side in FIG. 2, and the toner image is separated from the photoconductor 1 and conveyed to a fixing device (not shown). Therefore, the toner image is thermally fixed and then discharged to a discharge tray or the like outside the apparatus.

Further, the residual toner remaining on the photosensitive member 1 after the transfer is removed by a cleaning blade 9a provided in the cleaning unit 9, and the residual potential remaining on the photosensitive member 1 is removed. Is removed by the quenching lamp 10 (static elimination device), and a series of image forming processes are repeated again in preparation for the next charging by the charging roller 2.

FIG. 3 is a diagram showing a main part of FIG. 2 together with a control system. In this figure, 2 is the charging roller described above, and an elastic layer 22 made of epichlorohydrin rubber is attached to the outside of a conductive cored bar 21 made of iron or the like, and a surface of the elastic layer 22 on which hydrin rubber is dispersed in Lumiflon. The structure in which the layer 23 is applied is used.

Reference numeral 24 is a temperature detecting portion corresponding to the temperature detecting means A shown in FIG. 1. A temperature detecting element (for example, a thermistor) 26 is fixed to the tip of the conductive leaf spring 25, and the temperature detecting element 26 is attached. It is in contact with the surface of the charging roller 2 via a film material (not shown), and the temperature thereof is detected and notified to the control device 31. Reference numeral 27 denotes a cleaning member, which is normally separated from the charging roller 2 and contacts the charging roller 2 at a predetermined timing by a driving device (not shown) at a predetermined timing during a process according to the invention described later by the control device 31. To clean.

The control device 31 is a general-purpose microcomputer and controls each part in the copying machine as a whole. The control device 31 also functions as the applied voltage correction means C, the correction rule switching means D, the light quantity correction means E, and the potential correction means F shown in FIG. A voltage application device 32 applies a voltage to the conductive cored bar 21 of the charging roller 2 at a predetermined timing, whereby the surface 1a of the photoconductor 1 is applied.
Are uniformly charged.

Reference numeral 33 denotes a time-dependent change detecting device 33 corresponding to the time-dependent change detecting means B shown in FIG. 1, which detects a change with time of the photoconductor 1 and notifies the control device 31 of the change. In this embodiment, it is assumed that the change over time of the photoconductor 1 is its accumulated rotation time and that it is measured (detected) using a timer / counter.

Here, in this embodiment, for example, the toner density control by the P sensor 8 is performed every time a preset number of copies (image forming process) are completed. That is, after the endless belt 7a of the transfer device 7 is separated from the surface 1a of the photoconductor 1 by a driving device (not shown), the surface 1a of the photoconductor 1 is charged by the charging roller 2 to a predetermined voltage (-600V in this example). To do.

Next, P (not shown) from the exposure apparatus 11
By exposing with the light reflected by the sensor pattern plate (the plate on which the density control pattern is formed), an electrostatic latent image is formed,
After the electrostatic latent image is visualized by the developing roller 4a of the developing device 4 to form a density control pattern image, the toner adhesion amount is measured by the P sensor 8 such as a photo sensor. After controlling the toner replenishment from the toner replenishing device 14 to the developing device 4 so that the value becomes a preset value, the endless belt 7a of the transfer device 7 is brought into contact with the surface 1a of the photoconductor 1.

Further, since the electric resistance of the charging roller 2 largely changes due to the change of the temperature inside the apparatus and the charging potential changes due to the film thickness of the photoconductor 1 (= photoconductor capacity) being scraped, the controller 31 controls the temperature. Various processings such as correcting the voltage applied to the charging roller 2 by the voltage application device 32 are performed based on the detection values of the detection unit 24 and the time-dependent change detection device 33. These processings will be described in detail later.
Here, the VR correction processing (residual potential correction processing) and the VL correction processing (background potential control) generally performed in the copying machine will be briefly described.

The VR correction process and the VL correction process include a process of measuring the toner adhesion amount of the predetermined potential pattern image formed on the photoconductor 1 by the P sensor 8, and therefore the endless belt of the transfer device 7 is included. 7a is the surface 1a of the photoreceptor 1.
Must be separated from. So the first V
In the R correction processing, the driving device drives the endless belt 7 of the transfer device 7.
a is separated from the surface 1a of the photoconductor 1, and the subsequent processing is performed in that state.

That is, the photoreceptor 1 is charged by the charging roller 2.
After charging the surface 1a of the device to a predetermined voltage (-900V in this example), the eraser 3 removes the charge to form a residual potential pattern, which is visualized by the developing roller 4a (developing bias = 0V) of the developing device 4. After the image is formed, the toner adhesion amount is measured by the P sensor 8 to detect the residual potential, and the charge potential on the surface of the photoconductor 1 and the developing bias of the developing roller 4a during the image forming process are corrected according to the result. To do. That is, the charging potential and the developing bias are increased in proportion to the increase in the residual potential.

By this VR correction processing, even if the residual potential rises, the relationship between the developing bias of the developing roller 4a and the background potential of the surface of the photoconductor 1 is always (developing bias >> background potential).
As a result, the developing potential (= charging potential−developing bias) becomes constant, and an image of high ID free from background stain is maintained.

After that, VL correction processing is performed. That is,
After the surface 1a of the photoconductor 1 is charged to a predetermined voltage (-900V in this example) by the charging roller 2, the exposure device 11
Is exposed by light reflected by a VL pattern plate (a plate on which a low-density reference density pattern is formed) from FIG. 1 to form a reference potential pattern, which is visualized by the developing roller 4a of the developing device 4. After that, the toner adhesion amount is set to P
The reference potential is detected by measuring with the sensor 8, and the exposure lamp voltage (light amount) of the exposure device 11 during the image forming process is controlled so that the result becomes a preset value. The endless belt 7a is brought into contact with the surface 1a of the photoconductor 1.

By this VL correction processing, the halftone reproduction becomes constant and a stable image is maintained. By the way, each of the above correction processes is performed in the order of the VR correction process and the VL correction process. Therefore, when the reference potential pattern image (VL pattern image) is formed on the photoconductor 1 by the VL correction process, the VR correction process is performed. The image is formed with the corrected charging potential and the developing bias. As a result, the effect of residual potential on the image is further reduced.

FIGS. 4 and 5 are flow charts showing an example of the processing according to the present invention by the control device 31.
This routine starts when the main switch is turned on. First, in step 1, the flag FragB is initialized to "0", and in step 2, the temperature detected by the temperature detector 24 is the second set temperature T _{2 which} is predetermined. (20 ° C. in this example).

Then, the temperature detected by the temperature detector 24 is the second
If the temperature is not lower than the set temperature T2, the process immediately proceeds to step 5, but if it is lower than the set temperature T2, VR correction processing and VL are performed in step 3.
Perform correction processing and set flag FragB to "1" in step 4.
After that, it is determined in step 5 whether or not the copy job has started (whether or not a start key (not shown) is pressed), and if it starts, the copy operation for the first sheet is performed in step 6.

At the time of the VR correction processing and the VL correction processing, the voltage applied to the charging roller 2 is corrected in accordance with the temperature detected by the temperature detecting section 24, after referring to the correction rule described later. Each processing as described above is performed. 6A and 6B, the detection temperature of the temperature detection unit 24 and the voltage applied to the charging roller 2 when the charging voltage (surface voltage) of the photoconductor 1 is -900V and -600V, respectively. Of the RO in the control device 31 as a correction table.
It is stored in M.

Returning to the flow of FIG. 4, when the copy operation for the first sheet is completed, it is determined in step 7 whether the copy job is completed (whether the set number of copies has been reached). The copy operation for the second and subsequent sheets is performed, and when the copy job ends, the copy counter (not shown) is incremented (+ n) by the set number of copies n in step 8, and whether the flag FragA is "0" in step 9 To judge. The flag FragA is initialized to "0" at the start of use of this copying machine, and is initialized to "0" every time the photoconductor is replaced with a new one even if it becomes "1" thereafter. .

If the flag FragA is "0", the cumulative rotation time of the photoconductor 1 (assumed to be measured by a routine not shown) at step 10 reaches a preset time t (for example, 40 hours). Judging whether or not it reached,
When the set time t is reached, in step 11, the charging roller cleaning mode is set, and the cleaning member 27 shown in FIG. 3 is brought into contact with the charging roller 2 to clean the surface thereof, and then separated from the charging roller 2. As a result, charging failure (potential drop) due to dirt such as toner is prevented.

Next, in step 12, the correction rule to be referred to when correcting the voltage applied to the charging roller 2 according to the temperature detected by the temperature detector 24 is switched using the above-mentioned correction table. That is, in this embodiment, it is necessary to set the charging potential of the photoconductor at the time of VR correction processing and VL correction processing to -900V, so the voltage applied to the charging roller 2 is as shown in FIG.
The correction rule indicated by the solid line in (a) is switched to the correction rule indicated by the broken line.

Next, at step 13, VR correction processing and VL correction processing are performed. At this time, referring to the switched correction rule, the voltage applied to the charging roller 2 is also corrected according to the temperature detected by the temperature detector 24. After that, the flag FragA is set to "1" so that the processes of steps 11 to 14 are not performed thereafter, and then the process returns to the determination of whether the copy job has started in step 5, and the same processes as described above are repeated thereafter. .

On the other hand, in step 9, the flag FragA is "0".
If not, or if it is determined in step 10 that the cumulative rotation time of the photoconductor 1 has not reached the preset set time t, the process proceeds to step 15 in FIG.
It is determined whether the temperature detected by the temperature detector 24 is lower than a predetermined first set temperature T ₁ (18 ° C. in this example).

Then, the temperature detected by the temperature detector 24 is the first
If the temperature is not lower than the set temperature T _{1 of the} above, if it is lower, the charging roller cleaning mode is set in step 16 and the same processing as described above is performed, and then the flag is set in step 17.
It is determined whether FragB is "1". If it is "1", the temperature detected by the temperature detector 24 is the second set temperature T _{2 in} step 18.
It is determined whether or not there is the above.

Then, the temperature detected by the temperature detecting section 24 is the second
If the temperature is equal to or higher than the set temperature T _{2 of} , VR correction processing and VL correction processing are performed in step 19. At this time, the current correction rule is referred to, and the voltage applied to the charging roller 2 is also corrected according to the temperature detected by the temperature detector 24. Next, the flag FragB is set to "0" in step 20, the copy counter is reset to "0" in step 21, and the process returns to step 5.

When it is determined in step 17 that the flag FragB is not "1" or the temperature detected by the temperature detector 24 is not equal to or higher than the second set temperature T ₂ ,
In step 22, the count value of the copy counter (total number of copies) is set to a preset number of copies N (for example, 100).
(0 sheets) is determined, and only when the set number of copies N is reached, in step 23, VR correction processing and VL correction processing are performed as described above, and in step 24 the copy counter is reset to "0". After that, the process returns to step 5.

As described above, in the copying machine of this embodiment, the amount of change over time detected by the change-over-time detecting device 33 after the end of the copy job (image forming job) (photoreceptor 1
When the cumulative rotation time of the charging roller 2 exceeds a predetermined amount (setting time) set in advance, the cleaning member 27 cleans the charging roller 2 and a correction rule necessary for correcting the voltage applied to the charging roller 2 is set. After the switching, the VR correction processing and the VL correction processing described above are performed, and the subsequent copying process is performed based on the correction results. Therefore, the charging potential on the surface of the photoconductor 1 may change immediately after the correction rule is switched. In addition, the charging potential of the photoconductor 1 is always maintained at a constant value regardless of the environment inside the machine and the change over time, and stable image quality can be obtained.

Further, when the temperature detected by the temperature detector 24 is below a predetermined threshold value (set temperature T ₁ ), the cleaning member 27 cleans the charging roller 2, so that the following effects can be obtained. That is, a small amount of toner remains on the photoconductor 1 after cleaning by the cleaning unit 9, and the toner adheres to the photoconductor 1 mainly due to the image force of its own charge.
Although the number tends to increase due to low temperature and low humidity, by cleaning the charging roller 2 by the cleaning member 27, it is not necessary to detect the environment inside the apparatus by a new mechanism, and the charging member is not contaminated due to environmental changes with an inexpensive configuration. It can be effectively prevented.

Furthermore, since the VR correction processing and the VL correction processing are performed when the temperature detected by the temperature detection unit 24 falls below a predetermined threshold value (set temperature T ₂ ), the following effects are also obtained. That is, since the sensitivity of the photoconductor 1 becomes low at low temperature, the required exposure amount increases and the change becomes sharp as shown in FIG. 7, but if the exposure amount does not change from that at high temperature, an image obtained Shifts to the dark. However, each processing described above (including processing for increasing the exposure amount)
By doing so, it is possible to prevent the image from shifting to the dark due to the decrease in the sensitivity of the photoconductor at a low temperature.

Furthermore, since the VR correction processing and the VL correction processing are performed even when the temperature detected by the temperature detection unit 24 falls below the threshold value (set temperature T ₂ ) set in advance and then exceeds the threshold value, It is also possible to prevent the change of the image due to the change.

In the VR correction processing or the VL correction processing in this embodiment, the amount of toner adhered to the residual potential pattern image or the reference potential pattern image formed on the surface 1a of the photoconductor 1 is measured by the P sensor 8 to leave the residual amount. Although the quantity potential or the reference potential is detected, a surface potential meter for measuring the surface potential of the photoconductor 1 is provided in front of the developing device 4, whereby the residual potential before being visualized by the developing device 4 is provided. It is also possible to directly detect the potential of the pattern or the reference potential pattern, that is, the remaining potential or the reference potential.

Further, in this embodiment, as shown in FIGS. 4 and 5, both the VR correction processing and the VL correction processing are carried out at predetermined timings, but only the VL correction processing is carried out. You may As a result, when a selenium-based photoconductor is used, the charge potential of the photoconductor can always be maintained at a constant value, regardless of the internal environment of the device and the temporal change, as described above.

Although the embodiment in which the present invention is applied to a copying machine has been described above, the present invention is not limited to this, and other electrostatic printers such as laser printers, LED printers, liquid crystal shutter printers, and facsimile machines. It is also applicable to a photographic image forming apparatus.

[0057]

As described above, according to the image forming apparatus of the present invention, the charging potential of the photoconductor can be constantly maintained at a constant value regardless of the internal environment (usage environment) and the temporal change. The obtained image quality can be obtained. Claim 4
According to the invention, since the charging member is not contaminated with the toner, charging failure is reduced and more stable image quality can be obtained.

According to the fifth aspect of the present invention, it is not necessary to provide a new mechanism to detect the environment inside the machine. Therefore, it is possible to effectively prevent the charging member from being contaminated due to environmental changes with an inexpensive structure. According to the sixth aspect of the invention, it is possible to prevent the image from shifting to the dark due to the decrease in the sensitivity of the photoconductor at a low temperature. According to the invention of claim 7,
It is also possible to prevent a change in the image due to a change in the environment inside the machine.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing around a drum of a copying machine which is an embodiment of the present invention.

FIG. 3 is a diagram showing the main part together with a control system.

FIG. 4 is a flowchart showing a process according to the present invention by the control device of FIG.

FIG. 5 is a flowchart showing a continuation of the processing.

FIG. 6 shows a surface voltage of the photoconductor shown in FIG.
6 is a diagram showing the relationship between the temperature detected by the temperature detection unit and the correction amount of the voltage applied to the charging roller 2 when the voltage is set to 00 V and −600 V. FIG.

FIG. 7 is a diagram showing the relationship between the temperature of the photoconductor shown in FIG. 2 and the required exposure amount.

[Explanation of symbols]

 1: Photoconductor 2: Charging roller 3: Eraser 4: Developing device 7: Transfer device 8: P sensor 9: Cleaning unit 10: Quenching lamp 11: Exposure device 12: Registration roller 13: Pressure roller 14: Toner supply device 21: Conductive core bar 22: Elastic layer 23: Surface layer 24: Temperature detection part 25: Conductive leaf spring 26: Temperature detection element 27: Cleaning member 31: Control device 32: Voltage application device 33: Temporal change detection device A : Temperature detecting means B: Aging change detecting means C: Applied voltage correcting means D: Correction rule switching means E: Light quantity correcting means F: Potential correcting means

Claims (7)

[Claims] 1. A rotating photoconductor, a charging member that comes into contact with the photoconductor to uniformly charge the surface thereof, and an electrostatic latent image formed by exposing the surface of the photoconductor charged by the charging member. An exposure device that forms an image, a developing device that visualizes the latent image by adhering toner to the latent image with a developing roller, a transfer device that transfers the visualized toner image onto a transfer paper, and a charging member In an electrostatographic image forming apparatus including a cleaning member for cleaning a surface, a temperature detecting unit that detects a temperature of the charging member, a time change detecting unit that detects a time change of the photoconductor, and the temperature The applied voltage correction means for correcting the applied voltage to the charging member according to the detection temperature of the detection means, and the correction rule of the applied voltage according to the detection temperature by the means are provided for the lapse of time detected by the aging change detection means. Correction rule switching means for switching in accordance with the charge amount, and a voltage corrected by the applied voltage correction means is applied to the charging member to charge the surface of the photoconductor, and then exposed by the exposure device to expose a reference potential pattern. And a light amount correction means for detecting the potential and correcting the light amount of the exposure device during the image forming process. 2. The image forming apparatus according to claim 1,
By applying the voltage corrected by the applied voltage correction means to the charging member, the surface of the photoconductor is charged and then discharged, and the residual potential is detected to detect the charging potential of the surface of the photoconductor during the image forming process. An image forming apparatus comprising: a potential correcting unit that corrects a developing bias of the developing roller. 3. The temperature detected by the applied voltage correction means when the correction rule switching means has a time-dependent change amount detected by the time-dependent change detecting means after the image forming job is over, exceeds a predetermined amount. Means for switching the correction rule of the applied voltage according to the above, and the applied voltage correction means detects the temperature detection means by referring to the correction rule after the correction rule is switched by the correction rule switching means. The image forming apparatus according to claim 1, wherein the image forming apparatus is a unit that corrects a voltage applied to the charging member according to temperature. 4. The image forming apparatus according to claim 2,
An image forming apparatus, comprising means for cleaning the charging member with the cleaning member before the correction processing by the light amount correction means and the potential correction means is performed. 5. The image forming apparatus according to claim 1, wherein the cleaning member cleans the charging member when the temperature detected by the temperature detecting unit falls below a predetermined threshold value. An image forming apparatus comprising: 6. The light amount correction means and the potential correction means are means for performing the correction processing when the temperature detected by the temperature detection means falls below a predetermined threshold value. 4. The image forming apparatus according to item 4. 7. The light quantity correction means and the potential correction means are means for performing the correction processing when the temperature detected by the temperature detection means falls below a predetermined threshold value and then exceeds the threshold value. The image forming apparatus according to claim 2 or 4.